Latest questions from the community.
The poster spent two days trying to bring up a single-mode fiber link between an older Arista switch and a Cisco Catalyst 3650 (IOS-XE 3.7.5) with Cisco GLC-LH-SMD (SFP-LH-SMD) optics; the path runs through five patch cords in the same building and had been tested by the cabling contractor. At…
The poster, a new owner of a Cisco Nexus 93180YC-EX running NX-OS 7.0(3)I4(7), cannot bring up any 25G link. ipolex SFP28 DAC cables are recognized ('type is SFP-H25GB-CU1M', 'name is OEM', 'part number is SFP-H25G-CU1M', 'nominal bitrate is 25500 MBit/sec', 'DOM is not supported') but the port…
The poster runs temporary event networks and has twice hit heavy frame errors on 10G links between MikroTik and Cisco switches. About a year earlier a Cisco Catalyst 2960-S with 10G uplinks connected to a MikroTik CRS317-1G-16S+ showed CRC errors on the Cisco side and swapping cables did not help…
On a Cisco Nexus N9K-C93180YC-FX, QSFP-40G-SR-BD BiDi modules are not detected at all: nothing appears in the logs when they are inserted and they are absent from 'show interface transceiver', whereas QSFP-40GE-LR4 modules in the same ports are logged and listed normally. Several QSFP-40G-SR-BD…
The poster asked whether a 10G SFP+ SR or LR optic in one switch can auto-negotiate down to 1G to link over fiber with a 1G SFP in another switch, and if not, how to attach a handful of 1G optical connections from a 1G switch to a 10G switch. They understood that Cisco SFP+ optics run only at 10G…
In the poster's data center several Cisco CWDM SFP/GBIC links stopped working: some ports went err-disabled (one with link-flap as the cause) and others simply showed notconnect. Troubleshooting included shut/no shut, reseating the modules, moving the CWDM SFPs to other ports, replacing the patch…
The poster wanted to use a 40G QSFP+ to 4x10G SFP+ DAC breakout cable on a Cisco Catalyst 9500-32QC-E running IOS XE 17.6.4 (Bengaluru). The 'hw-module breakout' command is rejected; in global configuration only 'hw-module slot' and 'hw-module subslot' are offered. The switch is not running…
The poster could not find Cisco documentation describing how to set the frequency or ITU channel of a DWDM-SFP10G-C tunable 10G SFP+. A follow-up question asked whether a CPAK-100G-LR4 in a CRS-X 4-port 100GE LAN/OTN card could be tuned to a wavelength and connected directly to a ROADM of an…
A Cisco Catalyst 3850-24XS with an SFP-10G-LR (1310 nm) connects over a single-mode cross-connect to a Tier-1 carrier's layer-2 DWDM equipment in the same data center. When the carrier shuts the circuit down, TenGigabitEthernet2/0/23 goes 'down, line protocol is down (notconnect)' yet 'show…
Two Cisco Catalyst 3750-X switches (WS-C3750X-24P-L and WS-C3750X-48P-L) run identical code. A Cisco GLC-SX-MMD is detected normally in Gi1/1/1 of the first switch, but the second switch reports 'media type is Not Present' with 'link type is force-up' on Gi1/1/1, and 'show idprom interface Gi…
The poster (in a machine-translated post from the Spanish-language community) tried to connect two Cisco Business CBS350-24T-4X switches through their SFP+ ports using MikroTik XS+2733LC15D modules. No connectivity is established and the ports end up blocked by the switch's Link Flap Prevention…
The poster planned to install an Intel X520 adapter (Cisco PID N2XX-AIPCI01) into a Cisco UCS C240 server and use Cisco SFP-10G-SR or SFP-10G-LR transceivers, and asked whether the combination has compatibility problems. A later reader asked whether the Cisco SFP-H10GB-CU3M= twinax cable would work…
A friend of the poster bought several GLC-T copper SFPs sold as original Cisco, but their serial numbers had an unfamiliar format (00000MTC1719055H, 00000MTC171903XL and similar). 'show interface ethernet 1/45 transceiver sprom' on a Cisco Nexus 5596 lists the module as SFP-1000BASE-T, vendor name…
The poster connected a Dell server to a Cisco Catalyst C9500-48Y4C (IOS XE 17.9.3) using a Dell L56SF018-SD-R 3 m DAC (DAC-SFP-3M). The cable is not in Cisco's optics compatibility matrix, and 'show interface status' shows port TwentyFiveGigE1/0/35 as err-disabled. Logging shows…
The poster asked why third-party SFP modules stopped working after upgrading Cisco switches to IOS 15.2, whereas other vendors accept Cisco or other optics, and whether this is a technical limitation. No model, log output or interface details were given despite requests. In a later update the…
The poster wanted to use third-party SFP modules in a Cisco Catalyst 2960L-48TS (LAN Lite feature set, image c2960l-universalk9-mz.152-6.E2b). Entering 'service unsupported-transceiver' in global configuration mode only produced a command error because the CLI does not know the command on this…
The poster runs a Cisco Nexus 5000 with an N2K-C2232PP-10GE fabric extender. Three FEX-facing ports report 'sfp validation failed' with Cisco FET-10G modules. Following advice found online, the module was removed, the port speed set to 1000 and the module reinserted; the port was also shut/no shut…
While building a trunk between a Cisco Catalyst 3650-48PS and a Catalyst 3560CX-12PC using Cisco GLC-T copper SFPs at both ends, the 3560CX logged '%PHY-4-SFPNOTSUPPORTED: The SFP in Gi0/11 is not supported' and the link would not come up. The poster had already tried 'no errdisable detect cause…
The poster has a stack of two Cisco Catalyst 3850-48T switches, each fitted with a 2x1G/2x10G fiber uplink network module. Two 10G fiber links already run in slots 2/1/3 and 2/1/4. When a single-mode 1G SFP is inserted into 1G slot 2/1/1, the switch reports the module as unsupported and places the…
Two Cisco Catalyst C1200-48T-4X switches were connected back-to-back with Cisco SFP-10G-LR modules in the ge49/te1 SFP+ slots. Both switches recognize the transceivers, the interfaces are administratively up, both ends transmit light and the DOM optical values are good, yet no link is established…
The poster set up several new Cisco Catalyst 9300 switches fitted with C9300-NM-4G network modules, configured GigabitEthernet1/1/1 as a trunk and enabled it, but could not get a link with any of several SFPs. 'show interfaces' reports 'GigabitEthernet1/1/1 is down, line protocol is down…